Joining wings
 

Hey guys,

I am building a Sig Komander and have the wings all sheeted and set to go. The manual says that when joining the wings, to just Sig bond them.

Wouldn't that be a VERY weak point on the aircraft? I would think that when pulling some hard load factor, they would just fold on me. So I was thinking, should I Epoxy it at the joint, and then run a band of epoxy around the seam as if I was taping the joint?

These are foam wings with balsa sheeting.

Thanks for the help!

RE: Joining wings
 

when ever I have joined wings I use 30 min. epoxy on the joiners,the ply pieces that link the spars in each wing half.
I am not famillar with Sig Bond I would assume its there adhesive brand,having used carpenters wood glue,mainly Titebond, for years I would think it is plenty strong for joining the halves as well,keep in mind more glue doesn't make a better joint, enough adhesive to glue the wood and a good clamp job is the best way loading up on epoxy just adds extra weight not strength if your joint is tight you will have a strong wing in the end.

RE: Joining wings
 

Thanks Tim for your input. I just want to clarify that these are foam wings.

It just doesn't seem like epoxy sandwiched between the wings would be strong enough. Would my 'tape' idea be a good idea to do?

Here is a Kougar thread. In post 39 submikester, the builder, says that he 'glassed' the joint. Is 'glassing' it epoxying it? Is this what I should do? I am talking about the tape appearance around the seam in the first pic.

http://www.rcuniverse.com/forum/m_57..._2/key_/tm.htm

Thanks!

RE: Joining wings
 

Doh! I thought you were talking about built up wings I should have searched your for the model your building.
when most people refer to "glassing "they are talking about epoxy as the resin over a light grade of fiberglass usually around .75oz in weight it looks alot like silk fabric and adds strength as well as a base for painting.

a popular product is called Z-poxy its a thinner version than the stuff used in general building and construction,after joining the wing halfs you could also beef up the joint by using a slightly heavyer glass for strength in a 2-4" wide strip around the center of the wing.

again even when using epoxy for strenthening the joint more adhesive doesn't make the joint stronger,its the fiberglass that adds the strength,when you "wet" the fiberglass squeege the exess epoxy from the cloth so the cloth is tight to the surface you can always add more adhesive later if you feel theres not enough,as long as the cloth is saturated,and has the wet look, you should be fine and will have a strong center section when its dry.

I would think the sig glue is a foam specific adhesive so for the initial joining use the recomended adhesive, the glass at the center section is more of a insurance policy against failure.

RE: Joining wings
 

You can join them with any foam safe glue. Yes, it is a weak joint. You MUST fiberglass the center of the wing with foam/balsa construction because all of the strength and stresses are in the balsa skin. I would use about a 6" wide strip of 4oz fiberglass at a minimum. You can also laminate several layers of lighter glass, like 2oz. The pylon racers usually use about 3 layers of 2oz cloth, starting with a 6" wide strip, then a 4" wide strip, then a 2" wide strip. You can use laminating epoxy if you have it, it is the best choice but takes 24hrs. to set. You can also thin some 30 minute epoxy down and use that, this is usually what I do. Whatever you use, make sure you fully wet out the cloth, then soak up the excess resin with toilet paper or paper towel to keep the weight down to a minimum. You don't need to use one strip of cloth to do top and bottom surfaces, either. One over the top and one over the bottom is easier to keep smooth around the LE area. The best way to cut the cloth is with the fibers at a 45 degree bias, but straight is really OK for anything but the most severe usage.

Mark